If You’re Testing Blood Sugar with Diabetes, You Need to Know These 9 Rules

Testing blood sugar can provide valuable information to you and your doctor—if you do it correctly.

Monitoring your blood glucose may seem like a daunting chore at time, but it’s truly an insightful tool that allows you to learn more about your diabetes so you and your doctor can create a management plan that puts you in the driver's seat of your health.

The most common way to test your blood glucose, or blood sugar levels, is to use a lancet device to prick the skin to produce a small amount of blood. A test strip collects the drop, then you put the test strip into a machine called a glucometer, which reads the information on the test strip to give you the blood glucose reading.

According to CDC data, more than nearly 64 percent of adults with diabetes perform some daily self-monitoring of their blood glucose levels. (Note: The data doesn’t distinguish between adults with type 1, who must test their blood glucose every day, and those with type 2, who may not have to test their blood sugar depending on their own condition and how well its managed.)

Testing blood sugar is an empowering tool that really helps to identify and understand the effectiveness of lifestyle modifications, such as how a certain meal or exercise routine affects blood glucose, or how things like alcohol, hormonal shifts, illness, or even stress can trigger a spike in blood glucose levels.

Here are key things diabetes experts want you to know about testing your blood glucose.

1. How often to test depends on your meds

The frequency depends on what you and your doctor decide is right for you. However, adults with type 2 diabetes on multiple insulin injections will generally test blood glucose a few times day: in the morning after they’ve fasted overnight, before meals, at bedtime, and periodically in the middle of the night, says endocrinologist Akankasha Goyal, MD, an endocrinologist at NYU Langone Health.

For people with type 2 diabetes who are not taking insulin, your doctor may not recommend testing your blood sugar daily unless your diabetes is not well managed or unless you’re sick. Instead, they may advise you check two or three times a week to help identify factors that affect blood glucose, such as a new eating plan, medicine, or exercise. If you test your blood sugar and see, for example, that an hour after a meal, your levels are above 140 mg/dL, that’s a sign the meal wasn’t a great choice for you—maybe it had too many simple carbs and not enough fiber, fat, or protein.

But this is a highly personal decision that you and your doctor will make together, and how often and when you test your blood sugar may change over time, as well.

2. You may need to test more during certain situations

There’s nothing like a solid routine to keep your daily diabetes management predictable, but once in awhile things come up and you may need to test your blood sugar more often than usual. For example, if you’re under stress, have an illness, or are getting surgery, all of these things can affect blood glucose levels and you’ll want to monitor your blood glucose more often.

Taking new prescriptions, even if they aren’t directly related to diabetes management, may warrant more testing for a period of time to make sure they’re not having an impact on your blood sugar. For example, taking prednisone to help relieve arthritis pain is known to temporarily spike blood sugar levels.

And if you think you’re experiencing symptoms of low blood sugar or high blood sugar—or swings from one extreme to the other—you should test your blood sugar more often to help identify the factors that may be influencing the numbers (say, starting a starting a new workout plan).

3. Know when to seek medical attention after a blood sugar reading

You should have an acceptable blood glucose range based on your individualized care and recommendation from your doctor. However, Dr. Goyal recommends you call your doctor if you experience the following:

  • Repeated (more than three) blood sugar readings below the lower limit, usually 70 mg/dL (milligrams per deciliter is unit of measure that indicates the amount of glucose in a specific amount of blood)
  • Repeated (more than three) blood sugar readings above the upper limit, usually 250 mg/dL
  • Any blood sugar reading above 400 mg/dL
  • Nausea/vomiting
  • Other symptoms of very high or very low blood sugar

4. Don't play favorites (with the fingers where you test)

Thankfully, just a small drop of blood is needed to test blood glucose. Always start with a clean and dry finger, says certified diabetes educator Lucille Hughes, CDE, director of diabetes education for South Nassau Communities Hospital in Oceanside, New York. Although it may be easy to slip into a routine of using the same finger, it’s best not to favor just one finger or thumb. The repeated pricks may create a painful spot to test.

Using the sides of the tips of fingers will give you a sufficient amount of blood and can be less painful, says Hughes. One area to avoid: the middle of the fingertip pad. “This area is the most sensitive, since we have nerves there to help us feel hot and cold,” says Hughes.

It’s best to use the middle, ring, and pinky finger on each hand and rotate the finger sites. If you absolutely cannot stand the pain anymore on your fingers, talk to your doctor about alternative sites on the body like the abdomen or forearm. However, this requires a different kind of blood glucose meter and testing procedure.

5. Look for a less-painful lancet

A lancet is a tiny needle used to prick the skin to obtain a blood sample. The type of lancet you use will make a difference in how it feels when you poke your skin. You’ll feel a lot less pain by using new, thin lancets of 33-gauge or higher. A higher gauge creates a much smaller hole in the skin; therefore, less pain for you. It’s best to use a new lancet at least every day. “Using a new lancet is always best so you can be assured it is very sharp and you won’t feel it,” says Hughes. “As the lancet gets used, it gets bent, may splinter off into the skin, and may hurt more.”

Another way to reduce painful pricks is to choose a lancing device (a small device used to house the lancet) that has an adjustable tip. Set it on the lowest depth setting possible to help alleviate pain while still getting a good drop of blood. Be sure to dispose the lancets in a safe sharps container (available at a pharmacy) or a container made of hard plastic with a hard plastic lid that doesn’t allow needles to penetrate through.

6. Handle test strips with care

Test trips are small disposable strips of plastic that you insert into the glucose meter. When you prick your finger, the strip is used to collect the drop of blood. The strip is coated with glucose oxidace and interacts with the blood sample, which the meter reads and registers to give you your blood glucose reading.

Always keep the test strips in their original container. Never open a few to carry them in your purse or briefcase, as this can damage the strips. “Try to be meticulous when taking them out,” says Hughes. “Take one out and close the lid on the vial immediately as moisture in the air can damage the strips.” If strips come in individual foil packages, keep them in the package until you’re ready to use them.

7. Don't accidentally sabotage your reading

There are sneaky ways you can mess with your blood sugar reading and get an inaccurate result. This can affect the decisions you make regarding things like meals, exercise, and doses of diabetes medications, and increase your risk of having high or low blood sugar. In other words, not good. Hughes has few tips to get the most accurate readings.

  • Avoid alcohol or hand sanitizers on your fingertips that contain alcohol. Alcohol causes drying of the skin which could affect blood glucose reading if it mixes with blood when left on the skin while testing.
  • Keep test strips and the meter at room temperature. Exposure to extreme cold or heat can affect the reliability of the meter and strips.
  • Be mindful of the expiration date on the test strip container. Don’t use expired test strips, as this can affect the results of the reading. Once the test strip container is opened they will be effective for three to six months, depending on the brand you use.

8. Don't underestimate the power of an old-fashioned journal

Most blood glucose meters provide information that is downloadable and can generate handy reports that show when you’re in range or not hitting your target. But there’s more to discover when you keep a personal diabetes management journal too. “Maintaining a food journal has far-reaching benefits,” says Dr. Goyal. “Tracking your food, exercise, medications, and even stress helps uncover why your numbers may be out of range or help you to see what lifestyle choices helped you stay on target. Keep a journal for a month and then talk to your doctor or diabetes educator about you can get organized and set goals for blood sugar levels.

9. Consider continuous glucose monitoring

If you don’t want to test your blood sugar on your fingers multiple times a day, another option for some people may be a continuous glucose monitoring (CGM) system. It is a device you can insert yourself that uses a sensor under the skin, like the back of the arm for example, to monitor blood glucose. “They are accurate and reliable and decrease the number of times a patient has to stick their finger,” says Hughes.

Depending on the model, the continuous glucose monitor can be worn for a few days or up to about two weeks. The sensor can be worn in the shower or in the pool. However, a CGM doesn’t completely take the place of standard prick testing. The National Institute of Diabetes and Digestive and Kidney Diseases notes CGM glucose readings still need to be checked against a standard glucose meter twice a day.